8 ms·

Both theories are somewhat incomprehensible for normal human beings. The idea, that everythinw we know just came into existence at some point is as shocking as

by runxel 6y ago

Both theories are somewhat incomprehensible for normal human beings. The idea, that everythinw we know just came into existence at some point is as shocking as trying to think of something that has no beginning and no end. We humans are inherently bad in dealing with these terms.

Johnjonjoan 6y ago
You're right of course but I find the cyclic version so much more intuitive. The force from the big bang was imparted in an instant yet gravity is a constant force. IANAP but surely at some point the accumulative force of billions/trillions/... of years of gravity overcomes the force imparted by the big bang and the universe compresses into a singularity again? I'd really appreciate someone explaining why this isn't obviously the case.
- coldcode 6y ago
  I'm not sure we can ever tell the difference between the two models. Given the assumption that both produce a "boring" universe, and that models are never completely verifiable, it could be that either pathway appears the same to us at this point in time.
- tyfon 6y ago
  The issue with this view is that in the universe we see today the gravitational force is not strong enough to do what you describe here. There is acceleration of the expansion i.e. energy is added to the system (in the form of vacuum energy possibly). To say it in another way, the energy used to expand the universe today is not only the initial force imparted by the big bang but is added to as part of quantum processes in empty space. However as the universe expands, the amount of matter (dark + luminous) does not increase so the proportion of gravity/matter to dark energy (the force that accelerates the expansion) is getting lower and we get an acceleration. These observations exclude the possibility of a "big crunch". Disclaimer: I am a statistician not a cosmologist but this is how I have understood it.
  - Johnjonjoan 6y ago
    Cheers, I now understand why it's not such a clear case. I fear I may have many more harder to answer questions now though - Thanks none the less!
    - GioM 6y ago
      Take the idea a little further, to the end of the universe, and the rate of acceleration of expansion of space increases so much that stars become isolated from each other, then planets from stars, then molecules from each other, then atoms, and then quarks, the constituents of matter itself, and then.... An interesting thing happens. When you tear a quark away from it's antiquark, you get two quarks. The energy is equal to that required to bring another quark into existence. At this point, the rate of expansion is so vast that every quark in the universe has been forever isolated from one another, and then each bursts into a sea of high-energy quark-gluon plasma. The massive energy of expansion is rapidly consumed generating these quarks, and then the expansion slows, never stopping, but continues at a much slower rate. Wait... we've seen this before. A quark-gluon plasma, rapidly expanding from a single point, in a universe isolated from all others. Only expansion is required to generate new universes, forever.
      - deleted 6y ago
        [deleted]
- treeman79 6y ago
  Gravity is traveling at the speed of light. Space is expanding. Objects far apart are traveling away from each faster than the speed of light. Or more that the space between them is expanding faster then the speed of light. So those objects will never have any sort of interaction. Only ways around this if space itself start contracting. (No known way for this to happen). Or somehow the universe is a big circle, and going far enough brings you back to the starting point. Negative curvature. We don’t have any good theories on this. Some highly interesting ones that move the problem up a level. For Example one theory is our entire universe is inside a black hole created from the remains of a four dimensional hyper star. The math seems to work. Soo cool. But then where does the hyper star come from? It’s “turtles all the way down”, is the thought to lot of the best theories. Or everything is a simulation, again math kind of works. No direct evidence, but neat idea. But who’s hosting the sever that’s running the universe. Something from nothing problem is a real trouble maker.
  - Johnjonjoan 6y ago
    Objects far apart may be traveling faster than the speed of light but once the universe reaches equilibrium won't there be intermediate masses that gravity will be able to travel through? I was also under the impression that an expansion of space would just reduce the gradient of the gravity along that space and not inhibit its propagation. If like a bubble space has some form of surface tension then would there be a point that it can no longer expand? Gravity could then become dominant and force the contraction. -edit-> I guess that wouldn't contract the space though just the matter? I promise I'm not being pedantic or contrarian for the sake of it but to further my knowledge, thanks for your input!
    - fhars 6y ago
      There is no "equilibrium" the universe is moving towards, it is just expanding, and the "intermediate masses" are getting more spread out the more the universe expands. The expansion doesn't inhibit the propagation of gravity, it just makes the attraction between masses weaker and weaker the further they are apart, until they are so far apart that the space between them expands faster than the speed of light, at which moment they will no longer be able to interact with another, neither by light nor by gravity, and the contracting effect of gravity becomes weaker and weaker the larger the universe becomes. According to out current best cosmological model, Lambda-CDM (which, admittedly, is mostly a phenomenological model for things we only half understand, but still describes our current observations better than any competing model), gravity used to be the dominant force in the universe when it was smaller so that the masses were closer together until quite recently. But now it looks like the expansion, the "Lambda" term in "Lambda-CDM", the cosmological constant of general relativity, has become the dominant force in the universe, and the universe is slated to expand ever faster. It could start to contract if Lambda were closer to zero, but it currently doesn't look like it might move there. But then we don't know why Lambda it there at all and what causes it not to be zero in the first place, as everyone expected it to be until about two decades ago (Einstein himself thought of the introduction of the term into his theory as a blunder, as it would obviously be zero in any sane universe.)
- hacknat 6y ago
  The Universe can be infinite without being cyclic.
deleted 6y ago
[deleted]
sago 6y ago
I'm not the physicist (my mother was), but as I understand it the 'came into existence' is not part of the big bang model. Big bang only makes sense to a particular energy/time/space limit. All the energy that came to be all the universe already existed. What happened 'before that' doesn't even make sense. I was told that 'creation' type language is a misunderstanding of the big bang. Is that not still the way it works?
- simonh 6y ago
  The Big Bang theory itself doesn't answer the question of where the Universe came from, but I don't think it's stilly to ask what happened 'before' the Big Bang, or when the size of the Universe was near or below the Planck Scale. Relativity by itself predicts a singularity at a finite time in the past, at the beginning of the Big Bang. We know from Quantum Mechanics that Relativity is not complete though so the origin of the Universe and the nature of time through that process is still up in the air.
  - mensetmanusman 6y ago
    How can one speak of the size of the universe before the big bang if the concept of space-time was created during the event?
    - simonh 6y ago
      How do you know the concept of space-time was created during the event though? That's just an assertion. This theory, and the theory of conformal cyclic cosmology proposed by Roger Penrose do not have that feature, for example.
    - MacsHeadroom 6y ago
      Size and progression do not require space or time. The quantity of nodes in a branching tree of causal events can grow larger without time or space if there is no reccurance for any given state to be compared to another. From the "gods eye view" the tree "grows" even if there's no internal information which can be used to recover any space/time prior to reccurance.
state_less 6y ago
A circle doesn’t have a beginning or an end, yet folks seem to be okay dealing with them. Personally, I’m stumbling on understanding physical fields. This looks like another field is being added, which is nice in some sense, but why do we have the number of fields that we do and what conditions are needed to create/sustain physical fields?
- JamesSwift 6y ago
  The issue is not that a circle has no beginning and end, but what led to the creation of the circle in the first place? It didn't materialize from nothingness, I drew it on a paper.
  - state_less 6y ago
    Rather than materialize from nothing, every event would be connected to the next and if you proceed along the events, you'll eventually see the same/similar events again. Sort of like a circularly linked list.
    - pravus 6y ago
      Except now you have a winding number and the two circles aren't equivalent everywhere.
onion2k 6y ago
The idea, that everythinw we know just came into existence at some point is as shocking as trying to think of something that has no beginning and no end. It's only an issue if you think about space and time as separate things. I find it makes (a little) more sense when you understand that time is a function of spacetime. Therefore if you're happy with space not existing prior to the big bang (which people do seem to be OK with) then automatically time didn't exist either, and hence 'before the big bang' ceases to be a problem.
- simonh 6y ago
  That's just a semantic dodge to avoid answering phrasings of the question that use the term 'before'. However the comment you're replying to didn't use the 'before' phrasing. We can't dodge the broader question of how, or why the Universe came about in the particular form that it did so easily.
  - asdfasgasdgasdg 6y ago
    You can dodge further by saying that causality only exists in space time, so asking what "caused" the start of space time is incoherent. But, "it just did" has never been a satisfactory answer outside the halls of churches and seminaries, so this dodge continues to be unsatisfying.
    - mensetmanusman 6y ago
      The phrasing is worded wrong here: “it just did” has never been a satisfactory answer inside of churches or seminaries. That is why almost all the metaphysical discussion in these areas of human thought are around why we exist (in human terms). “it just did” has been a satisfactory answer outside of churches or seminaries. This is why almost all discussion of why there is something rather than nothing in secular academia is ‘meh, impossible to know, don’t worry about it’
- istjohn 6y ago
  This is what gets me. I can imagine no space and no time. But in a reality without space and time, by definition, nothing happens. There is nothing to act or be acted on. There is no timeline by which to order cause and effect. But the Big Bang posits that, in fact, something did happen: space and time began. The most incredible event imaginable occurred in the most impossible circumstance. It just doesn't compute for me. It's much easier for me to imagine that time is just turtles all the way down.
Santosh83 6y ago
Actually I find an absolute beginning and an absolute ending more troublesome to think about. It is easier to accept that in reality while everything keeps changing and recycling, the sum total has always been.
- stOneskull 6y ago
  why there is something at all, i think we can never know. but yeah, likewise. it seems energy/things existing for infinity is the only thing that makes sense, and something coming from nothing is impossible. i think a part of us wants there to be a beginning but there really can't be.
  - aspaviento 6y ago
    On the other hand, maybe this bouncing is completely deterministic and we are meant to do the exact same things we did trillions of years ago.
    - ssijak 6y ago
      If the universe has infinite bounces than yes, there are countless universes in the past and future where I type this same message.
  - ssijak 6y ago
    “Why there is something at all?” The only answer I can satisfy myself with at least a bit is that there is no option for nothing to exist.
Allower 6y ago
Probably because its a really weak theory..folks in the scientific community are grasping at straws far more than they are willing to admit. For some sense, just notice how rare it is for any so-called "expert" to preface their statements with "as far as we know" or some other similarly appropriate hedge.

by runxel 6y ago

Johnjonjoan 6y ago

You're right of course but I find the cyclic version so much more intuitive. The force from the big bang was imparted in an instant yet gravity is a constant force. IANAP but surely at some point the accumulative force of billions/trillions/... of years of gravity overcomes the force imparted by the big bang and the universe compresses into a singularity again? I'd really appreciate someone explaining why this isn't obviously the case.

coldcode 6y ago
I'm not sure we can ever tell the difference between the two models. Given the assumption that both produce a "boring" universe, and that models are never completely verifiable, it could be that either pathway appears the same to us at this point in time.
tyfon 6y ago
The issue with this view is that in the universe we see today the gravitational force is not strong enough to do what you describe here. There is acceleration of the expansion i.e. energy is added to the system (in the form of vacuum energy possibly). To say it in another way, the energy used to expand the universe today is not only the initial force imparted by the big bang but is added to as part of quantum processes in empty space. However as the universe expands, the amount of matter (dark + luminous) does not increase so the proportion of gravity/matter to dark energy (the force that accelerates the expansion) is getting lower and we get an acceleration. These observations exclude the possibility of a "big crunch". Disclaimer: I am a statistician not a cosmologist but this is how I have understood it.
- Johnjonjoan 6y ago
  Cheers, I now understand why it's not such a clear case. I fear I may have many more harder to answer questions now though - Thanks none the less!
  - GioM 6y ago
    Take the idea a little further, to the end of the universe, and the rate of acceleration of expansion of space increases so much that stars become isolated from each other, then planets from stars, then molecules from each other, then atoms, and then quarks, the constituents of matter itself, and then.... An interesting thing happens. When you tear a quark away from it's antiquark, you get two quarks. The energy is equal to that required to bring another quark into existence. At this point, the rate of expansion is so vast that every quark in the universe has been forever isolated from one another, and then each bursts into a sea of high-energy quark-gluon plasma. The massive energy of expansion is rapidly consumed generating these quarks, and then the expansion slows, never stopping, but continues at a much slower rate. Wait... we've seen this before. A quark-gluon plasma, rapidly expanding from a single point, in a universe isolated from all others. Only expansion is required to generate new universes, forever.
    - deleted 6y ago
      [deleted]
treeman79 6y ago
Gravity is traveling at the speed of light. Space is expanding. Objects far apart are traveling away from each faster than the speed of light. Or more that the space between them is expanding faster then the speed of light. So those objects will never have any sort of interaction. Only ways around this if space itself start contracting. (No known way for this to happen). Or somehow the universe is a big circle, and going far enough brings you back to the starting point. Negative curvature. We don’t have any good theories on this. Some highly interesting ones that move the problem up a level. For Example one theory is our entire universe is inside a black hole created from the remains of a four dimensional hyper star. The math seems to work. Soo cool. But then where does the hyper star come from? It’s “turtles all the way down”, is the thought to lot of the best theories. Or everything is a simulation, again math kind of works. No direct evidence, but neat idea. But who’s hosting the sever that’s running the universe. Something from nothing problem is a real trouble maker.
- Johnjonjoan 6y ago
  Objects far apart may be traveling faster than the speed of light but once the universe reaches equilibrium won't there be intermediate masses that gravity will be able to travel through? I was also under the impression that an expansion of space would just reduce the gradient of the gravity along that space and not inhibit its propagation. If like a bubble space has some form of surface tension then would there be a point that it can no longer expand? Gravity could then become dominant and force the contraction. -edit-> I guess that wouldn't contract the space though just the matter? I promise I'm not being pedantic or contrarian for the sake of it but to further my knowledge, thanks for your input!
  - fhars 6y ago
    There is no "equilibrium" the universe is moving towards, it is just expanding, and the "intermediate masses" are getting more spread out the more the universe expands. The expansion doesn't inhibit the propagation of gravity, it just makes the attraction between masses weaker and weaker the further they are apart, until they are so far apart that the space between them expands faster than the speed of light, at which moment they will no longer be able to interact with another, neither by light nor by gravity, and the contracting effect of gravity becomes weaker and weaker the larger the universe becomes. According to out current best cosmological model, Lambda-CDM (which, admittedly, is mostly a phenomenological model for things we only half understand, but still describes our current observations better than any competing model), gravity used to be the dominant force in the universe when it was smaller so that the masses were closer together until quite recently. But now it looks like the expansion, the "Lambda" term in "Lambda-CDM", the cosmological constant of general relativity, has become the dominant force in the universe, and the universe is slated to expand ever faster. It could start to contract if Lambda were closer to zero, but it currently doesn't look like it might move there. But then we don't know why Lambda it there at all and what causes it not to be zero in the first place, as everyone expected it to be until about two decades ago (Einstein himself thought of the introduction of the term into his theory as a blunder, as it would obviously be zero in any sane universe.)
hacknat 6y ago
The Universe can be infinite without being cyclic.

deleted 6y ago

[deleted]

sago 6y ago

I'm not the physicist (my mother was), but as I understand it the 'came into existence' is not part of the big bang model. Big bang only makes sense to a particular energy/time/space limit. All the energy that came to be all the universe already existed. What happened 'before that' doesn't even make sense. I was told that 'creation' type language is a misunderstanding of the big bang. Is that not still the way it works?

simonh 6y ago
The Big Bang theory itself doesn't answer the question of where the Universe came from, but I don't think it's stilly to ask what happened 'before' the Big Bang, or when the size of the Universe was near or below the Planck Scale. Relativity by itself predicts a singularity at a finite time in the past, at the beginning of the Big Bang. We know from Quantum Mechanics that Relativity is not complete though so the origin of the Universe and the nature of time through that process is still up in the air.
- mensetmanusman 6y ago
  How can one speak of the size of the universe before the big bang if the concept of space-time was created during the event?
  - simonh 6y ago
    How do you know the concept of space-time was created during the event though? That's just an assertion. This theory, and the theory of conformal cyclic cosmology proposed by Roger Penrose do not have that feature, for example.
  - MacsHeadroom 6y ago
    Size and progression do not require space or time. The quantity of nodes in a branching tree of causal events can grow larger without time or space if there is no reccurance for any given state to be compared to another. From the "gods eye view" the tree "grows" even if there's no internal information which can be used to recover any space/time prior to reccurance.

state_less 6y ago

A circle doesn’t have a beginning or an end, yet folks seem to be okay dealing with them. Personally, I’m stumbling on understanding physical fields. This looks like another field is being added, which is nice in some sense, but why do we have the number of fields that we do and what conditions are needed to create/sustain physical fields?

JamesSwift 6y ago
The issue is not that a circle has no beginning and end, but what led to the creation of the circle in the first place? It didn't materialize from nothingness, I drew it on a paper.
- state_less 6y ago
  Rather than materialize from nothing, every event would be connected to the next and if you proceed along the events, you'll eventually see the same/similar events again. Sort of like a circularly linked list.
  - pravus 6y ago
    Except now you have a winding number and the two circles aren't equivalent everywhere.

onion2k 6y ago

The idea, that everythinw we know just came into existence at some point is as shocking as trying to think of something that has no beginning and no end. It's only an issue if you think about space and time as separate things. I find it makes (a little) more sense when you understand that time is a function of spacetime. Therefore if you're happy with space not existing prior to the big bang (which people do seem to be OK with) then automatically time didn't exist either, and hence 'before the big bang' ceases to be a problem.

simonh 6y ago
That's just a semantic dodge to avoid answering phrasings of the question that use the term 'before'. However the comment you're replying to didn't use the 'before' phrasing. We can't dodge the broader question of how, or why the Universe came about in the particular form that it did so easily.
- asdfasgasdgasdg 6y ago
  You can dodge further by saying that causality only exists in space time, so asking what "caused" the start of space time is incoherent. But, "it just did" has never been a satisfactory answer outside the halls of churches and seminaries, so this dodge continues to be unsatisfying.
  - mensetmanusman 6y ago
    The phrasing is worded wrong here: “it just did” has never been a satisfactory answer inside of churches or seminaries. That is why almost all the metaphysical discussion in these areas of human thought are around why we exist (in human terms). “it just did” has been a satisfactory answer outside of churches or seminaries. This is why almost all discussion of why there is something rather than nothing in secular academia is ‘meh, impossible to know, don’t worry about it’
istjohn 6y ago
This is what gets me. I can imagine no space and no time. But in a reality without space and time, by definition, nothing happens. There is nothing to act or be acted on. There is no timeline by which to order cause and effect. But the Big Bang posits that, in fact, something did happen: space and time began. The most incredible event imaginable occurred in the most impossible circumstance. It just doesn't compute for me. It's much easier for me to imagine that time is just turtles all the way down.

Santosh83 6y ago

Actually I find an absolute beginning and an absolute ending more troublesome to think about. It is easier to accept that in reality while everything keeps changing and recycling, the sum total has always been.

stOneskull 6y ago
why there is something at all, i think we can never know. but yeah, likewise. it seems energy/things existing for infinity is the only thing that makes sense, and something coming from nothing is impossible. i think a part of us wants there to be a beginning but there really can't be.
- aspaviento 6y ago
  On the other hand, maybe this bouncing is completely deterministic and we are meant to do the exact same things we did trillions of years ago.
  - ssijak 6y ago
    If the universe has infinite bounces than yes, there are countless universes in the past and future where I type this same message.
- ssijak 6y ago
  “Why there is something at all?” The only answer I can satisfy myself with at least a bit is that there is no option for nothing to exist.

Allower 6y ago

Probably because its a really weak theory..folks in the scientific community are grasping at straws far more than they are willing to admit. For some sense, just notice how rare it is for any so-called "expert" to preface their statements with "as far as we know" or some other similarly appropriate hedge.